[CGF] Get rid of passing redundant VTable pointer around in CodeGenFunction::InitializeVTablePointer[s]

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188909 91177308-0d34-0410-b5e6-96231b3b80d8
Move the logic for selecting the last feature in the command line to the driver.

This is a partial revert of r188817 now that the driver handles -target-feature
in a single place.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188910 91177308-0d34-0410-b5e6-96231b3b80d8